The government has put Australia on a higher state of alert after receiving information of possible terrorist threats. Authorities say British and U.S. interests in Australia could be targets.

The Australian government says it does not have any detailed information about the latest terrorist threats but it not taking any chances.

Attorney-General Daryl Williams has asked for increased security on airlines and at key but yet unidentified installations. Mr. Williams says he wants to reassure Australians that national security arrangements are in place and that the security services have a well-coordinated and rehearsed anti-terrorist plan.

Australia has been on a high state of security alert since the September 11 suicide attacks in the United States. Australia is considered a potential terrorist target because of its commitment to the U.S.-led war on terrorism. Canberra has deployed more than 1,500 troops and military hardware in Afghanistan.

There has been concern that one important part of Australia's security blanket, undercover air marshals, would not be in place before the busy Christmas holiday period. One airline has said it will be at least Friday before it is even possible to deploy the new guards.

The Australian Protective Service controls the squad of 22 flying armed officers, which completed its training last week. The force will carry weapons with ammunition not capable of penetrating the fuselage of an aircraft.

The program will cost tens of million dollars, but there is confusion about who will pay for it. Both the federal government and the airlines insist it is the other's responsibility.

Australia's Civil Aviation Safety Authority has renewed its warnings about additional security at airports over the Christmas holidays.

Sunday, detectives questioned four men about a breach of security at the country's biggest airport in Sydney. They were arrested after climbing a perimeter fence around the runway. They have been released and so far have not been charged.